diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index 1bca52fd2..74fc65d36 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -680,7 +680,7 @@ mod pure_builtins {
             return Ok(e);
         }
 
-        let v = e.to_str()?;
+        let v = e.to_contextful_str()?;
         Ok(Value::Bool(v.has_context()))
     }